Process of applying powder to a rotating object

ABSTRACT

A method of spraying powder from nozzles onto the outer periphery of the pipe while the pipe is rotated about its longitudinal axis. The spray nozzle or nozzles are spaced from the outer periphery of the pipe and at the optimum angle with respect to the transverse or cross-sectional configuration of the pipe for providing the most efficient and complete coating or covering of the object.

Unite States Patent Neal Feb. 12, 1974 1 PROCESS OF APPLYING POWDER TO A3,407,099 10/1968 $611611 117/1054 ROTATING OBJECT 3,439,649 4/1969Probst et a1 1 17/17 3,155,545 11/1964 Rocks et a1. 117/17 [75]Inventor: D nnis Neal, Tulsa, a 3,581,922 6/1971 Versoy 117/17 2,428,99110/1947 Ransburg 117/17 [73] Assgnee" g g Tulsa 3,536,514 10/1970 LaFave 61. a1 117/17 1 Fi1ed= 31, 1971 Primary Examiner-William 1). ManinAppl. No.: 129,869

U.S. Cl ..l17/16,117/17,117/18, 117/20,117/21,117/24,117/105.4,118/310,118/314,118/315,118/316,118/320,

Int. Cl B05b 5/2, 844d 1/94 Field of Search. 117/16, 17, 20, 21, 24,104R, 117/105.4, 18; 118/621, 627, 308, 310, 311, 312, 314, 315, 316, 320,630

References Cited UNITED STATES PATENTS Stanley et a1. 117/17 AssistantExaminerM. Sofocleous Attorney, Agent, or Firm-William S. Dorman 5 7ABSTRACT A method of spraying powder from nozzles onto the outerperiphery of the pipe while the pipe is rotated about its longitudinalaxis. The spray nozzle or nozzles are spaced from the outer periphery ofthe pipe and at the optimum angle with respect to the transverse orcross-sectional configuration of the pipe for providing the mostefficient and complete coating or covering of the object.

6 Claims, 12 Drawing Figures PAIENT'EB rm 1 2 I974 sum 1 or z .g A y Fig4 Fig. 5

Fig 3 DENNIS NEAL INVENTOR.

WMJW

ATTORNEY Pmarim 3.791.842

SHEET 2 [IF 2 so so 2 y l 2 O E 50 2 a 4 5 e 7 s 9 060 90 I20 150DISTANCE IN INCHES LOCATION,

DEGREES SEPARATION 7 Fig. 8

50 60 60 5 U 2 5 5 E 50 6 so E 50 LL c: IJJ LL NUMBER OF GUNSORIENTATION, AIR PRESSURE, PSI

DEGREES Fig. 9 Fig.10 Fig. 11

so u Z 2: U I so it DENNIS NEAL INVENTOR.

20 3o 40 so so 70 BY LINEAR SPEED, FT./M|N. A E

Fig. 12

ATTORNEY PROCESS OF APPLYING POWDER TO A ROTATING OBJECT This inventionrelates to improvements in coating objects and more particularly, butnot by way of limitation, to a method of applying powder to the surfacesof a rotating object.

It is well known that the service life of pipes, whether disposedunderground or otherwise, is hampered or greatly lessened due to theelement surrounding the pipe. For example, the underground or buriedmetallic pipes are subjected to a great amount of external corrosionwhich results from a natural flow of electric current caused by thereaction between the metal surfaces and chemicals in the soil or watersurrounding the structure. The electric current will flow from the metalto the adjacent soil and back to the metal, thus making the metallicstructure an anode at the point where the current leaves the metallicstructure and as the current flows from the pipe, minute particles ofthe metal are carried into the soil, thereby causing pitting of thepipe. This is commonly called electrolysis and over a period of time thepipe may become severely damaged and require replacement. This isparticularly disadvantageous with very large diameter pipe lines whichare used for transporting natural gas at high pressures. weakening ofthe pipe due to corrosion or other reasons can lead to explosions,causing severe damage and occasionally loss of life. i

There are several methods utilized today for reducing the damage due tocorrosion or electrolysis, such as eathodic protection, or externalcoating of the pipe for protection thereof. The external coatings areapplied to either buried structures or to those structures disposedabove the ground, and are generally considered to be advantageous forseveral reasons in that the coating may provide a more universal andlasting protection for the pipe than the cathodic protection method.However, many of the coatings presently available have certaindisadvantages in that the comparatively rough handling of the pipeduring installation, and the like, frequently chips the coating orbreaks the coating and as a result deterioration of the metal canresult. Common practice is to both coat the pipe and protect the pipecathodically. Cathodic protection, however, frequently causes thecoating to fail. Consequently, there has been a great study and effortput forth in the development of coatings for pipe, and particularlyplastic coatings which will overcome these disadvantages. For example,one such coating known under the trade name Nap- Gard has been developedby the Napko Corporation which has proven to be extremely efficient anddesirable for the exterior coating of the pipe. This particular coatingmaterial is tough and has a great resistance to deterioration undercathodic protection. Nap-Gard is a high molecular weight cross linkedpolymer whose basic polymeric structure consists of linearized phenolictype units, further described in the Napko Industrial Coating Divisionpublication SA-258 dated April 1967. This coating material requires theapplication of two coats of material, with one of the coatingspreferably being the application thereof in powdered form. Of course, itwill be apparent that the coating must be applied to the externalsurface of the pipe in a manner for completely covering thereof toproduce the necessary protection of the pipe, and as a result it isextremely important to apply the powdered form thereof in an efficientmanner for a complete covering of the surface being coated.

The present invention contemplates a novel method of applying powder toa rotating object. such as a pipe rotating about its longitudinal axis,in a manner wherein a complete and efficient coating or covering of theobject is assured. The powder is sprayed onto the outer periphery of theobject through nozzles or spray guns which have been particularly spacedand arranged with respect to the distance from the object to assure anefficient application of the powder. lt is to be noted that theefficiency of the coating is the percentage of powder delivered from theguns which actually adheres to or stays on the object. The distance ofthe guns from the object has a major effect upon the coating efficiencyand is directly related to the spray pattern. In addition, the locationof the banks of guns significantly affects the efficiency of thecoating, whereas the specific number of the guns appears to have arelatively minor effect on the coating efficiency. The orientation ofthe guns also produces a major effect on the coating efficiency, and anorientation of the guns leading into the direction of rotation of theobject greatly improves the coating efficiency. In addition, whereas airpressure has a slight by definite effect on the efficiency, it is notedthat the efficiency is greater with the use of lower air pressure. Thelineal speed of the rotating object appears to be a major effect of thecoating efficiency, it is considered that this may be somewhatillusionary, since the efficiency increase related to lineal speed maybe the result of less repulsion of the particles from the surface havinga thinner, more diffuse coating. Furthermore, the electrostatic chargeis also a major condition in the effect of the coating efficiency. Thus,in the present method of applying powder to a rotating object, carefulselection of the spacing between the guns, the distance of the guns fromthe object, and the angular disposition of the guns or orientation ofthe guns with respect to the object are particularly selected to producean efficient application of the powder not heretofore attainable.

It is an important object of this invention to provide a novel method ofapplying powder to a rotating object such as a pipe section beingrotated about its longitudinal axis.

lt is another object of this invention to provide a novel method ofapplying powder to a rotating object by spray guns wherein the spacingof the guns with respect to the object is particularly selected foroptimum efficiency of the coating of the object.

Another object of this invention is to provide a novel method ofapplying powder to a rotating object by spray guns wherein the spacingbetween the guns is particularly selected for optimum coatingefficiency.

Still another object of this invention is to provide a novel method ofapplying powder to a rotating object wherein an angular position ororientation of the guns with respect to the object is particularlyselected for optimum coating efficiency.

A further object of this invention is to provide a novel method ofapplying powder to a rotating object which is simple in operation andefficient in results.

Other and further objects and advantageous features of the presentinvention will hereinafter more fully appear in connection with adetailed description of the drawings in which:

FIG. 5 is a schematic side elevational view of one type of spray gundepicting a spray pattern as used during the application of powder inaccordance with the invention.

FIG. 6 is a schematic plan view of a pair of adjacent spray gunsdepicting a spray pattern as used during the application of powder inaccordance with the invention.

FIGS. 7 through 12 are graphic representation of the experimentsrelating to coating efficiency as related to:

FIG. 7 distance of guns to object;

FIG. 8 angular separation of banks of guns;

FIG. 9 number of guns;

' FIG. 10 angular orientation of each gun with respect to object;

FIG. 11 driving air pressure for guns; and

FIG. 12 linear speed of outer periphery of pipe past guns.

The experiments resulting in the present invention were conducted on 30inch diameter pipe which was cleaned prior to the coating operation, anda coating similar to that disclosed in the Richard C. Stanley et al.co-pending applications Ser. No. 52,638, filed July 6, 1970, entitledMethod for Coating Pipe, now Pat. No. 3,687,706; and Ser. No. 56,822,filed July 21, l970, entitled Method and Means for Coating Pipe, nowPat. No. 3,687,704 and with which I am familiar, was the basis for theexperimentation in the application of the powder to the outer peripheryof the pipe. The pipe was checked by proper personnel for acceptability,and the rate at which pipe could be properly cleaned was determined andcorrelated to the wheelabrator formula 1 sq. ft./HP/min. for white metalcleaning.

The cleaned pipe was heated over the 4 inch by 4 inch row of Blu-Surfburners, and the time required to heat the pipe to a temperature of 450F. was measured. The effects of pipe rotation rate, the effects of thedistance of the pipe from the burner, the effects of the wall thicknessof the pipe on the heating rate were also determined. A family of curveswas then generated using this data to show heating rates for differentwall thicknesses and different pipe diameters. The tests and experimentsof the powder application were then conducted to determine the effect ofseveral application variables on the efficiency of the coating. Ashereinbefore set forth, the efficiency of coating is the percentage ofpowder delivered from the guns which actually stays on the pipe. Thefollowing variables were studied during the experimentation:

l. The distance of the gun from the outer periphery of the pipe. 2. Thelocation of the banks of guns around the outer periphery of the pipe.

3. The number of guns. 4. The orientation (or angular dispostion) of theguns (leading or trailing the direction of pipe rotation.

5 5. The air pressure utilized in the guns.

6. The electrostatic charge.

The guns in each bank of guns were spaced longitudinally along the pipeon 9 inch centers, and each of the above variables was evaluatedseparately, as will be hereinafter set forth in detail.

With regard to the iocation of the gun banks, and referring particularlyto FIGS. 1 and 8, reference character 10 schematically indicates a pipediameter, reference character 12 indicates a first or top bank of guns,and reference character 14 schematically indicates a second or bottombank of guns. As hereinbefore set forth, the guns in the banks 12 and 14are spaced longitudinally along the pipe 10 on 9 inch centers, and thelocation of the banks 12 and 14 around the pipe 10 with respect to eachother were tested at a plurality of angular positions therebetween, withthe location of the banks being indicated by positions on clock. Asshown in FIG. 1, the top bank 12 is located at or 12 oclock, whereas'thebottom bank 14 is located at 240 in the clockwise direction, or 8oclock. The graph depicted in FIG. 8 shows the correlation betweencoating efficiency and the location of the banks of guns as referencedby degrees of separation.

The coating efficiency appears to be affected significantly by thepositioning or location of the gun banks 12 and 14 around the outercircumference of the pipe 10, and as clearly shown in FIG. 8, theoptimum efficiency was obtained with a spacing of substantially ninetydegrees therebetween. This was a rather surprising result, and the datawere determined through the use of only two banks of guns. It isadmitted that the use of three banks of guns may provide differentresults.

The number of guns provided appears to have a minor effect on thecoating efficiency, as shown in FIG. 9. However, it is believed thatthis may be due to the effect of the position of the guns in thedifferent banks of guns rather than any real effect due to the number ofguns.

The distance of the guns from the outer periphery of the pipe, however,has a major effect on the coating efficiency, as is clearly shown inFIG. 7. The distance of the guns from the pipe is also directly relatedto the spray pattern as shown in FIGS. and 6. The experimental datashows a marked improvement with the guns spaced 5 inches from the outerperiphery of the pipe, and at a greater distance than the 5 inches, thespray patterns from adjacent guns overlap causing severe turbulence. Asshown in the graph in FIG. 7, the optimum distance appears to be from 4/2 inches to 5 inches for guns spaced on 9 inch centers. Of course, gunson different center line spacing would have different optimum distances.

Referring particularly to FIGS. 5 and 6, the nozzles or spray tips 16and 18 are longitudinally spaced with respect to the pipe with thecenterlines 20 and 22 thereof, respectively, spaced substantially nineinches apart. The spray patterns from the nozzles 16 and 18 are shown inside elevation in FIG. 5 and in plan view in FIG. 6 as indicated at 24and 26, respectively. It will be readily apparent that in FIG. 6, thatthe spray patterns 24 and 26 begin to overlap at a distance ofapproximately four and one-half inches forward or away from the outerextremity of the nozzles 16 and 18, as shown at 28. At a distance of 5inches from the nozzles 16 and 18 there is a slight overlapping of thespray patterns, but the coating efficiency is relatively high, even atthe 5 inch distance from the pipe.

With regard to the angular position or orientation of the guns withrespect to the pipe, FIGS. 2, 3, 4 and 10, depict a variety of gunorientations. As shown in these Figures, the pipe is indicated as beingrotatable about its longitudinal axis in a clockwise direction asindicated by the arrow A. The gun, indicated schematically at G isdepicted in FIG. 2 as being positioned normal to the pipe, whereas thegun G is orientated from the normal position at a negative angle aleading into the direction of rotation in FIG. 3, and at a positiveangle a trailing the direction of rotation in FIG. 4.

The orientation of the guns has a major effect on the coatingefficiency, as particularly shown in FIG. 10. An orientation leadinginto the direction of rotation markedly improves the coating efficiency.This effect was not optimized, however, and it is possible that evenbetter results may be obtainable. It appears likely that the optimumangle of the guns depends on two factors, namely the rate of piperotation and the distance of the guns from the pipe.

As shown in FIG. 11, the air pressure utilized in conjunction with thenozzles or guns appears to have a slight but definite effect, withbetter coating efficiency being obtained at the lower air pressure. Itshould be noted that the general level of efficiency is much higher inthese data points because the pipe was coated at a lineal speed ofapproximately 67.7 feet per minute during this particular testingoperation.

As will be seen from an inspection of FIG. 12, the lineal speed of thepipe moving past the guns appears to have a major effect upon thecoating efficiency. However, this is believed to be somewhat illusorysince the coatings obtained were not complete but barber poled. It isbelieved that this increase in efficiency is caused by less repulsion ofthe powder particles from the surface of the pipe with the thinner morediffuse coating, a phenomenon demonstrated by Resins Technical Center.Under normal conditions it is doubtful if this improvement in efficiencywill actually be observed.

The testing also indicated that electrostatic charge has a major effectupon the coating efficiency, causing a difference of approximatcfl fiperceglhgisglgr e v iHEiTE e tFaf EYTaFQ particles are required when thistype of equipment is used.

Based on the results of this testing of powder application or coating ofrotating objects with powder it has been found that a relationshipexists between coating efficiency and the location of the banks of gunsaround the outer periphery of the pipe; the spacing of the guns from thepipe; and the orientation of the guns with respect to the pipe. Theseresults were surprising since there has been nothing in the prior art toindicate that these variables would produce such an increase in coatingefficiency. An orientation of the guns in a negative angular direction,or leading into the direction of the rotation of the object beingcoated, in combination with a spacing between the guns related to thedistance of the guns from the outer periphery of the pipe whereby only aslight overlapping of spray patterns is achieved, and furtherconsideration being given to the circumferential location of the gunbanks around the outer periphery of the pipe provides a coatingefficiency in the application of powder to a rotating object notheretofore obtained.

Whereas the present invention has been described in particular relationto the drawings attached hereto, it should be understood that other andfurther modifications, apart from those shown or suggested herein, maybe made within the spirit and scope of this invention.

What is claimed is:

I. A process of applying powder to a rotating object which comprisesutilizing at least one bank of spray guns for applying the powder to theouter periphery of the object, disposing each bank of spray gunscircumferentially about the outer periphery of the object with respectto the rotational axis of the object, spacing the guns longitudinallyalong the length of each bank, locating each bank of guns at a selecteddistance from the outer periphery of the object with relation to thelongitudinal spacing between the guns of each bank so that there is aslight overlap of spray pattern of the powder from adjacent guns of eachbank, orientating the angular position of the guns in a negative angulardirection leading into the direction of the rotation of the object andspraying the powder onto the object while rotating the object about itslongitudinal axis.

2. A process of applying powder to a rotating object as set forth inclaim 1 wherein there are two banks of spray guns, said banks beingcircumferentially spaced around the outer periphery of the objectapproximately apart.

3. A process of applying powder to a rotating object as set forth inclaim 1 wherein the orientation of the guns is approximately 15 leadingfrom the normal into the direction of rotation of the object.

4. A process of applying powder to a rotating object as set forth inclaim 1 and including placing an electrical charge on the particles ofthe powder being applied to the object.

5. A process of applying powder to a rotating object which comprisesutilizing a pair of banks of spray guns for applying the powder to theouter periphery of the object, disposing the banks of gunscircumferentially around the outer periphery of the object at a spacingof approximately 90 between the banks, spacing the guns longitudinallyalong the length of the banks, placing the guns at a selected distancefrom the outer periphery of the object in coordination with thelongitudinal spacing between the guns whereby the spray patterns of theadjacent guns of each bank slightly overlap upon impinging the outerperiphery of the object, orientating the angular position of the guns ina plane perpendicular to the longitudinal axis of the object at an angleof approximately 15 from the normal leading into the direction ofrotation of the object, and spraying the powder onto the object whilerotating the object about its longitudinal axis.

6. A process of applying powder to a rotating object as set forth inclaim 5 and including placing an electrical charge on the particles ofthe powder being applied to the object.

i i I I! k

2. A process of applying powder to a rotating object as set forth inclaim 1 wherein there are two banks of spray guns, said banks beingcircumferentially spaced around the outer periphery of the objectaPproximately 90* apart.
 3. A process of applying powder to a rotatingobject as set forth in claim 1 wherein the orientation of the guns isapproximately 15* leading from the normal into the direction of rotationof the object.
 4. A process of applying powder to a rotating object asset forth in claim 1 and including placing an electrical charge on theparticles of the powder being applied to the object.
 5. A process ofapplying powder to a rotating object which comprises utilizing a pair ofbanks of spray guns for applying the powder to the outer periphery ofthe object, disposing the banks of guns circumferentially around theouter periphery of the object at a spacing of approximately 90* betweenthe banks, spacing the guns longitudinally along the length of thebanks, placing the guns at a selected distance from the outer peripheryof the object in coordination with the longitudinal spacing between theguns whereby the spray patterns of the adjacent guns of each bankslightly overlap upon impinging the outer periphery of the object,orientating the angular position of the guns in a plane perpendicular tothe longitudinal axis of the object at an angle of approximately 15*from the normal leading into the direction of rotation of the object,and spraying the powder onto the object while rotating the object aboutits longitudinal axis.
 6. A process of applying powder to a rotatingobject as set forth in claim 5 and including placing an electricalcharge on the particles of the powder being applied to the object.